Ignition plug



T. R. ARDEN Sept, 27, 1949.

IGNITION PLUG Fi1ed.Jan. l6

INVENTOR,

Patented Sept. 27, 1949 Thomas Raymond Arden, Danbury, Conn., as-

signor to Bard-Parker Company, Inc., Danbury, Conn, a corporation of NewYork Application January 16, 1948, Serial N 0. 2,7 51

1 Claim. (01. 123-445) This invention relates to ignition plugs forinternal combustion engines, and has particular reference toimprovements in ignition plugs of the so-called glow type which areheated by the fuel charges which they ignite, as distinguished from theelectric are or so-called spark type.

One object of the invention is to provide an ignition plug of the glowtype which is generally similar to, and may readily be used to replace,ignition plugs of the spark type, and which, in addition, embodies asimple, practical construction such that its heating or glow element mayreadily be heated electrically for engine starting purposes.

Another object of the invention is to provide an ignition plug of theglow type in which the heating or glow element is contained ina smallchamber which is located in and opens through the inner end of the baseor inner end portion of the plug, whereby it is disposed to effectivelyserve its purpose of igniting fuel charges and, at the same time, isprotected against flow over the same of fuel charges to be ignited andhence against chilling by the latter. Further in this connection, an--other object of the invention is to form said chamber, or at least theopen end thereof, of such small size that gases flowing into the enginecylinder and over the open end of said chamber are not caused by thelatter to partake of turbulence.

A further object of the invention is to provide an ignition plug of theglow type with a substantially spherical head for the temporary andconvenient attachment to the plug of a battery circuit terminal clip ofthe popular, so-called alligator type when it is desired to electricallyheat the heating element of the plug for engine starting purposes, andto so construct said head as to preclude the possibility of attachingthe terminal clip thereto in a manner such that it might contact anyportion of the engine and thereby become grounded.

With the foregoing and other objects in View, which will become morefully apparent as the nature of the invention is better understood, thesame consists in an ignition plug embodying the novel features ofconstruction, combination and arrangement of parts as are illustrated byway of example in the accompanying drawings and as will be hereinaftermore fully described and claimed,

In the accompanying drawings, wherein like sulating material.

outer bore 12 against the washer ll and acts characters of referencedenote corresponding parts in the different views:

Figure 1 is a side elevation of an ignition plug constructed inaccordance with the invention, a portion of an engine to which it is tobe applied and a terminal clip for connection with the same beingshownby dotted lines;

Figure 2 is a central, longitudinal section through the plug; and

Figure 3 is a top plan view of the plug showing the terminal clip indotted lines.

Referring to the drawings in detail, it will be observed that thepresent ignition plug is general- 1y similar in appearance to anordinary sparkplug and has the inner end portion of its body [0exteriorly threaded in accordance with conventional spark plug designand practice, whereby it is adapted to be used interchangeably with, andto replace, ignition plugs of the spark type.

Extending axially of the plug body l0 into the same from its inner andits outer ends are inner and outer bores II and I2, respectively, whichcommunicate with each other-at their inner ends. The outer bore I2 is ofgreater diameter than the inner bore II and thereby there is provided anoutwardly facing shoulder [3 at the junction of the inner ends of saidbores.

Extending from the outer end of the plug inwardly through the outer borel2 and a short distance into the inner bore l I, is an electricalconductor M of rod form, the outer end portion of which is threaded andwhich is provided, near its inner end, with an annular enlargement orflange l5.

Seated upon the shoulder I3 is a washer N5 of suitable electricalinsulating material in the center of which is a hole through which theinner end portion of the conductor It extends into the bore I I.

The enlargement or flange [5 of the conductor I4 is seated upon thewasher l6, while engaged upon said conductor outwardly of saidenlargement or flange l5 and seated upon the latter, is a second washerll of suitable electrical in- A nut is is threaded into the through thelatter and the flange l5 and the washer l6 and the shoulder l3 to securethe conductor I4 firmly to the plug body In against any 1 possibilit ofits endwise movement relative thereto. Lateral or sidewise movement ofsaid conductor relative to said plug body is prevented said conductor.

Against the outer end of the plug body In is seated a washer 19 ofsuitable electrical insulating material and against this washer isseated the inner end of a ball head 20 which is threaded upon the outerend portion of the conductor l4 and which constitutes an electricalterminal to have engaged therewith a terminal clip 2| of an electricalheating circuit.

The inner bore H constitutes a chamber in which is disposed a heatabsorbing element 22 which preferably, but not necessarily, is in theform of a helix wound from wire having a high electrical resistance. Thehelix 22 is disposed coaxially with respect to the bore or chamber IIand at one end is welded or otherwise suitably connected to the innerend of the conductor l4 and at its other end is welded or otherwisesuitably connected to the inner end of the plug body In.

When the ignition plug is applied to an internal combustion engine, theplug body It) is, of course, grounded with respect to the engine.Accordingly, when one side of an electrical heating circuit is connectedto the engine and the other side of said circuit is connected to theplug terminal 20, the element 22 is included in the circuit and therebybecomes heated.

The element 22 is electrically heated only for engine starting purposes,for after the engine is started, the heat of combusion of its fuelcharges maintains said element heated whereby it is effective to ignitesubsequent charges. In this connection, the present plug is especiallyadvantageous for use in connection with internal combustion enginesemployed as power plants for model or toy airplanes, boats, landvehicles, and the like, since it not only relieves the same of theburden of carrying the weight of batteries and other accessories ofspark ignition apparatus, but avoids the uncertainties of sparkignition. In other words, after an engine equipped with the presentignition plug has been started, the electrical apparatus for initiallyheating the heating element 22 may be disconnected from the plug.Consequently, electrical apparatus for initially heating the element 22need never be mounted in or carried by a model aircraft the engine ofwhich is equipped with the present ignition plug.

Since the element 22 is disposed entirely within the bore or chamber ll,as shown, it is disposed outside the path of flow of fuel chargesentering the combustion chamber of an engine upon which the plug is usedand therefore is not cooled or chilled by the fuel charges. Moreover, inpractice, the bore or chamber H is so very small (in the neighborhood ofonly about one eighth of an inch in diameter) that fuel charges flowing;across the inner end of the plug are practically unaffected by saidchamber insofar as creation of turbulence in the fuel charges isconcerned. As the fuel charges are compressed, they are, of course,heated. Consequently, when they are forced into the bore or chamber llduring the final part of the compression stroke of the engine 4 piston,they are so hot as to have little, if any, cooling eifect upon theelement 22.

Terminal clips of the so-called alligator type, as illustrated in thedrawings, are well known and may be employed for connecting ignitioncircuit wires to spark plug terminals. When such clips are used for thispurpose with ignition plugs as heretofore constructed, it has been foundthat the clips tend to gravitate to downwardly and inwardly disposedpositions relative to the plugs such that they contact parts of theengines and create short circuits. In this connection, the ball head 20of the present plug substantially insures a positive grip of a clip ofthe alligator type therewith in any attitude of the clip relative to theball head so that there is little or no danger of the clip changing itsposition relative to the ball head due to gravitation alone or assistedby vibration. Moreover, the present ball head is provided with a base 23which acts as a stop, engageable by a terminal clip of the alligatortype engaged with said ball head, to limit the zone in which the clipmay be engaged with said ball head in different angular positionsrelative thereto and to thereby preclude the possibility of the clipcontacting any part of an engine with which the present plug is used. Inother words, the base 23 limits application of a terminal clip of thealligator type to the ball head 22 to a substantially hemispherical zonethe base of which is located at the inner side of said ball head.Therefore, there is little or no chance of a terminal clip engaged withthe ball head 2!) ever producing a short circuit by contacting part ofan engine with which the present plug is used.

From the foregoing description considered in connection with theaccompanying drawing, it is believed that the construction and operationof the present ignition plug will be clearly understood and itsadvantages appreciated. It is desired to point out, however, that whileonly a single, specific embodiment of said plug has been illustrated anddescribed, the same is readily capable of modifications and changeswithin the spirit and scope of the invention as defined in the appendedclaim.

I claim:

An ignition plug comprising a plug body having its inner end portionexteriorly threaded for threaded engagement in an opening in an internalcombustion engine, said plug body having therein inner and outer boresconnected with each other and opening through its inner and outer ends,respectively, said inner bore being of lesser diameter than said outerbore whereby a shoulder is formed at the inner end of the latter, anelectrical conductor extending through said larger bore into saidsmaller bore, a flange on said conductor, a washer of electricalinsulating material seated against said shoulder inwardly of said flangeand having said flange seated thereon, a second washer of electricalinsulating material dispmed outwardly of said flange and seated thereon,a nut threaded in said outer bore against said second washer and actingthrough said washers and said flange and said shoulder to clamp saidconductor firmly to said plug body, said washers closely fitting saidouter bore and snugly embracing said conductor whereby they act to holdsaid conductor coaxially with respect to said bores and spaced from thewalls defining the sides of the latter, a heat retaining elementdisposed in said smaller bore and connected at spaced points to saidconductor and said plug body, whereby it is adapted to be heated 5 6electrically and also by the heat of combustion of fuel charges which itignites to ignite subsequent REFERENCES CITED fuel charges, said nutbeing disposed entirely The following references are of record in theWithin said outer bore, a washer of electrical infi Of this p n sulatingmaterial seated against the outer end 6 UNITED of said plug body andclosing the outer end of STATES PATENTS said outer bore, and anelectrical terminal ele- Number Name Date "ment threaded on the outerend portion of said 1,359,514 tfOO V- 1920 conductor against said lastmentioned washer 1,590,891 ny June 29, 1926 and serving to clamp thelatter tightly against 10 1,532,314 u qv st June 14, 1927 the outer endof said plug body. 2,138,301 owie Nov. 29, 1938 THOMAS RAYMOND ARDEN.

